Railcar retarders are utilized in railway classification yards in conjunction with a "hump" over which a string of cars is pushed. The railcars are then individually, or in groups, allowed to accelerate down the hump and through appropriate switching networks to their ultimate destination. As the cars accelerate down the hump, it is necessary to maintain the speed of travel under certain limits in accordance with the railcars rolling resistance, distance to be traveled and various other factors. Because light railcars must usually be given the greatest acceleration to reach their most distant location in a classification yard, the hump is built high enough, or the yard is profiled, to cause light railcars to reach a sufficient velocity to carry them to their furthest point. Railcar retarders are then added to reduce the speed of the heavier cars, so that the railcars will not be damaged and will not be subject to excessive wheel lift and derailment.
One type of retarder exhibits a shock absorber-like construction which is mounted at various intervals to the rails in a yard. Such retarders are comprised of a hydraulic unit which exerts a variable resistive force upon deflection of a portion of the unit by the outer edge or flange of a wheel rolling over the rail. To ensure proper function of the retarders, it is necessary for the performance of the retarders to be periodically tested once the retarders have been installed on the tracks.
Heretofore, the most fundamental method of field testing retarders was effected by a maintenance person using his or her foot to compress the retarder and develop a "feel" to determine if the installed retarder has enough resistance. This method is unsafe, inaccurate, and unsanctioned in many classification yards.
A spring-loaded lever device exists for the purpose of measuring the resistive force in a retarder. The spring is compressed on a color-coded cylinder to give a rough measure of the resistive force left in the retarder. The existing tester requires that the user clear ballast under the base of the rail, slide a hinged lever arm under the base of the rail and rotate the device over the retarder and head of the rail. The user then pushes down on a handle and tries to read the color code located on the cylinder. All of this is done with the user crouching very close to ground level, approximately 7 inches thereabove. Normally there are hundreds of retarders to test on a single track in a classification yard. By using this existing method, this prior art device would take upward of two minutes to check one retarder.
Until this invention, no accurate method of checking the resistive force in an installed retarder was available. With the introduction of the spring-loaded lever device, an individual retarder could be checked. However, this method was cumbersome, inaccurate and impractical for checking a large population of retarders. This prior art device also could only check one brand of retarders, so that it had very limited application. Before the invention, the only way to find a "bad" retarder, or to check the condition of any retarder, was to remove the retarder from service and somehow push on it and then using an educated guess, determine whether the unit is acceptable or unacceptable.
Accordingly, it is desirable to provide an on-site testing device and method which allows for repeatable preventive maintenance by safely and accurately testing the amount of resistive force left in an installed retarder. It is also desirable to provide a testing device and method which will enable one to diagnose retarder performance within a short interval of time and without removing the retarder from the rail. Further, it is desirable to provide a testing device and method which permits a user to test a retarder in the field while standing in an upright position.